This works on drizzle and the other difficulties if you’re fast enough…
How to Get Flawless
Get to Rallypoint Delta
Try to get there fast but still pick up some items (especially topaz brooch)
Buy the TC-280 Prototype
Maybe even buy a couple of turrets so that most enemies will just die while you charge the teleporter.
Start the Teleporter
Hopefully you get an easy boss that the TC-280 can quickly kill or one that you can quickly kill by yourself.
If the topaz brooch doesn’t work, then try using the Engineer’s shield.
Sorry if this fails but you should be able to get it in a couple tries.